During the last decade, a great deal has been learned about the replicative cycle of human hepatitis B virus (HBV), a DNA virus that causes acute and chronic hepatitis, liver cirrhosis, and hepatocellular carcinoma. The latter complication causes over one million deaths worldwide every year. Although there are there is at least a number of distinct differences between HBV and HIV, one notable resemblance between these two human pathogenic viruses in that their replicative cycle involves an obligate RNA intermediate and a reverse transcription step in the cytoplasm.